Priority load sharing for electrical power systems having multiple power sources

ABSTRACT

Example electrical power systems include an output for supplying a DC output voltage to a load, a first power source connected with the output to supply DC power to the load, and a second power source connected with the output to supply DC power to the load. The electrical power system is configured to supply DC power to the load using only the first power source when a demand of the load is less than an output capacity of the first power source, and the second power source is configured to maintain an enabled on-state when only the first power source is supplying DC power to the load. Additional electrical power systems and methods are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit and priority of U.S. ProvisionalApplication No. 62/650,025, filed Mar. 29, 2018. The entire disclosureof the above application is incorporated herein by reference.

FIELD

The present disclosure relates to priority load sharing for electricalpower systems having multiple power sources.

BACKGROUND

This section provides background information related to the presentdisclosure which is not necessarily prior art.

Some power systems having multiple power sources implement priority loadsharing by turning different power sources on and off as needed in apriority sequence (e.g., by using enable/disable commands, etc.). Forexample, a power source having a higher priority may supply power to aload when a demand of the load is low, and an additional power sourcehaving a lower priority can be enabled to supply additional power to theload when the demand of the load increases.

Other power systems implement priority load sharing by connecting anddisconnecting different power sources from a load as needed in apriority sequence (e.g., by controlling switches that connect/disconnecta power source to/from an output bus, etc.).

SUMMARY

This section provides a general summary of the disclosure, and is not acomprehensive disclosure of its full scope or all of its features.

According to one aspect of the present disclosure, an electrical powersystem includes an output for supplying a DC output voltage to a load, afirst power source connected with the output to supply DC power to theload, and a second power source connected with the output to supply DCpower to the load. The electrical power system is configured to supplyDC power to the load using only the first power source when a demand ofthe load is less than an output capacity of the first power source, andthe second power source is configured to maintain an enabled on-statewhen only the first power source is supplying DC power to the load.

According to another aspect of the present disclosure, an electricalpower system includes an output for supplying a DC output voltage to aload, a first power source connected with the output to supply DC powerto the load, and a second power source connected with the output tosupply DC power to the load. The electrical power system is configuredto supply DC power to the load using only the first power source when ademand of the load is less than an output capacity of the first powersource, and the first power source and the second power source are eachconfigured to selectively supply DC power to the load without receivinga command from the load, and without disconnecting one of the powersources from the output.

According to another aspect of the present disclosure, a method ofprioritizing load sharing in an electrical power system is disclosed.The electrical power system includes an output for supplying a DC outputvoltage to a load, a first power source connected with the output, and asecond power source connected with the output. The method includessupplying DC power to the load using only the first power source when ademand of the load is less than an output capacity of the first powersource, and supplying DC power to the load using both the first powersource and the second power source when a demand of the load is greaterthan an output capacity of the first power source. The method alsoincludes maintaining the second power source in an enabled on-state whenonly the first power source is supplying DC power to the load.

Further aspects and areas of applicability will become apparent from thedescription provided herein. It should be understood that variousaspects and features of this disclosure may be implemented individuallyor in combination with one or more other aspects or features. It shouldalso be understood that the description and specific examples herein areintended for purposes of illustration only and are not intended to limitthe scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure.

FIG. 1 is block diagram of an electrical power system according to oneexample embodiment of the present disclosure.

FIG. 2 is block diagram of an electrical power system having three powersources, according to another example embodiment of the presentdisclosure.

FIG. 3 is a bar graph of a droop V-I characteristic of the power sourcesof FIG. 2.

FIG. 4 is block diagram of an electrical power system including threepower sources using an active current share control, according toanother example embodiment of the present disclosure.

FIG. 5 is a bar graph of an active current control V-I characteristic ofthe power sources of FIG. 4.

FIG. 6 is a block diagram of an electrical power system including apower supply unit and a battery backup unit using droop current sharecontrol, according to another example embodiment of the presentdisclosure.

FIG. 7 is a block diagram of an electrical power system including apower supply unit and a battery backup unit using active current sharecontrol, according to another example embodiment of the presentdisclosure.

FIG. 8 is a line graph of an example priority power sharing V-Icharacteristic of the power system of FIG. 6.

FIG. 9 is a front view of an electrical power system includingrack-mountable units, according to another example embodiment of thepresent disclosure.

Corresponding reference numerals indicate corresponding featuresthroughout the several views of the drawings.

DETAILED DESCRIPTION

Example embodiments are provided so that this disclosure will bethorough, and will fully convey the scope to those who are skilled inthe art. Numerous specific details are set forth such as examples ofspecific components, devices, and methods, to provide a thoroughunderstanding of embodiments of the present disclosure. It will beapparent to those skilled in the art that specific details need not beemployed, that example embodiments may be embodied in many differentforms and that neither should be construed to limit the scope of thedisclosure. In some example embodiments, well-known processes,well-known device structures, and well-known technologies are notdescribed in detail.

The terminology used herein is for the purpose of describing particularexample embodiments only and is not intended to be limiting. As usedherein, the singular forms “a,” “an,” and “the” may be intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. The terms “comprises,” “comprising,” “including,” and“having,” are inclusive and therefore specify the presence of statedfeatures, integers, steps, operations, elements, and/or components, butdo not preclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof. The method steps, processes, and operations described hereinare not to be construed as necessarily requiring their performance inthe particular order discussed or illustrated, unless specificallyidentified as an order of performance. It is also to be understood thatadditional or alternative steps may be employed.

Although the terms first, second, third, etc. may be used herein todescribe various elements, components, regions, layers and/or sections,these elements, components, regions, layers and/or sections should notbe limited by these terms. These terms may be only used to distinguishone element, component, region, layer or section from another region,layer or section. Terms such as “first,” “second,” and other numericalterms when used herein do not imply a sequence or order unless clearlyindicated by the context. Thus, a first element, component, region,layer or section discussed below could be termed a second element,component, region, layer or section without departing from the teachingsof the example embodiments.

Spatially relative terms, such as “inner,” “outer,” “beneath,” “below,”“lower,” “above,” “upper,” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. Spatiallyrelative terms may be intended to encompass different orientations ofthe device in use or operation in addition to the orientation depictedin the figures. For example, if the device in the figures is turnedover, elements described as “below” or “beneath” other elements orfeatures would then be oriented “above” the other elements or features.Thus, the example term “below” can encompass both an orientation ofabove and below. The device may be otherwise oriented (rotated 90degrees or at other orientations) and the spatially relative descriptorsused herein interpreted accordingly.

Example embodiments will now be described more fully with reference tothe accompanying drawings.

A power system according to one example embodiment of the presentdisclosure is illustrated in FIG. 1, and indicated generally byreference number 100. As shown in FIG. 1, the electrical power system100 includes an output 102 for supplying a DC output voltage to a load104, a first power source 106 connected with the output 102 to supply DCpower to the load 104, and a second power source 108 connected with theoutput 102 to supply DC power to the load 104.

The electrical power system 100 is configured to supply DC power to theload 104 using only the first power source 106 when a demand of the loadis less than an output capacity of the first power source 106, and thesecond power source 108 is configured to maintain an enabled on-statewhen only the first power source 106 is supplying DC power to the load104.

For example, the first power source 106 may have a primary prioritysetting that causes only the first power source 106 to supply DC powerto the load 104 when a demand of the load is less than an outputcapacity of the first power source 106. The first power source 106 maybe configured to regulate the DC output voltage in a constant voltageregulation mode when the demand of the load 104 is less than the outputcapacity of the first power source 106, and to enter a constant currentor constant power mode when the demand of the load 104 exceeds theoutput capacity of the first power source 106.

The second power source 108 may include a secondary priority settingthat causes the second power source 108 to supply DC power to the load104 only when the demand of the load 104 exceeds the output capacity ofthe first power source 106. The second power source 108 may beconfigured to regulate the DC output voltage in a constant voltageregulation mode while the first power source 106 is operating in theconstant current or constant power mode.

As described above, the system 100 provides a load sharing schemebetween the first power source 106 and the second power source 108 whereeach power source 106 and 108 has a different priority level (i.e., thefirst power source 106 has a higher priority level than the second powersource 108).

The first power source 106 operates in a constant voltage regulationmode while the demand of the load 104 is below the output capacity(e.g., a maximum output capacity, etc.) of the first power source 106.Once the demand of the load 104 exceeds the output capacity of the firstpower source 106, the first power source 106 enters a constant currentor constant power mode (e.g., a constant power protection mode).

For example, the constant voltage regulation mode may include a closedcontrol loop to maintain the DC output voltage of the output 102 at aspecified (e.g., preset) value. In some cases, a power converter (e.g.,a switched-mode power supply (SMPS), etc.) of the first power source 106may sense the DC output voltage and adjust a duty cycle, a frequency,etc. of the power converter to maintain the DC output voltage at thespecified value.

If the demand of the load 104 increases to exceed an output capacity(e.g., a rated output current) of the power converter, the converter mayenter the constant power mode as described above. In the constant powermode, the power converter of the first power source 106 may control itsduty cycle, frequency, etc. to decrease output voltage as the outputcurrent demand increases to maintain a constant output power. Theconstant output power may be represented by multiplying the outputvoltage and the output current, and may be equivalent to rated outputpower.

The constant current mode may inhibit a power source from exceeding itsrated current when the demand of the load 104 exceeds an individualpower source capacity (e.g., when multiple power converters areoperating in parallel). A power converter may enter the constant currentmode when the demand of the load 104 increases to reach a maximumcurrent capacity of the power converter. At this point, a duty cycle,frequency, etc. of the power converter may be controlled to maintain aconstant output current, which may be equivalent to a maximum allowedoperating current limit of the power converter.

Once the demand of the load 104 exceeds the output capacity of the firstpower source 106 and the first power source 106 enters a constantcurrent or constant power mode, the second power source 108 starts todeliver power to the load 104 in a priority load sharing arrangementwith the first power source 106. The priority load sharing between thefirst power source 106 and the second power source 108 may include droopcurrent share control, active current share control, etc.

For example, the second power source 108 may be configured to startsupplying DC power to the load 104 in response to the demand of the load104 increasing from a value less than the output capacity of the firstpower source 106 to a value greater than the output capacity of thefirst power source 106. The second power source 108 may be configured tostop supplying DC power to the load 104 in response to the demand of theload 104 decreasing from a value greater than the output capacity of thefirst power source 106 to a value less than the output capacity of thefirst power source 106.

Additionally, or alternatively, the first power source 106 may beconfigured to switch from the constant voltage regulation mode to theconstant current or constant power mode in response to the demand of theload 104 increasing from a value less than the output capacity of thefirst power source 106 to a value greater than the output capacity ofthe first power source 106. The first power source 106 may be configuredto switch from the constant current or constant power mode to theconstant voltage regulation mode in response to the demand of the load104 decreasing from a value greater than the output capacity of thefirst power source 106 to a value less than the output capacity of thefirst power source 106.

FIG. 2 illustrates an electrical power system 200 according to anotherexample embodiment of the present disclosure. The electrical powersystem 200 is similar to the electrical power system 100 of FIG. 1, butthe electrical power system 200 includes a third power source 210.

Specifically, the electrical power system 200 includes an output 202 forsupplying a DC output voltage to a load 204, a first power source 206connected with the output 202, a second power source 208 connected withthe output, and the third power source 210 connected with the output202.

The third power source 210 may have a tertiary priority setting wherethe third power source 210 supplies DC power to the load 204 only whenthe demand of the load 204 exceeds the output capacity of the firstpower source 206 and an output capacity of the second power source 208(e.g., a combined output capacity of the first and second power sources206 and 208).

The third power source 210 is configured to regulate the DC outputvoltage in a constant voltage regulation mode while the first powersource 206 is operating in the constant current or constant power modeand the second power source 208 is operating in a constant current orconstant power mode. The third power source 210 is configured tomaintain an enabled on-state during a period where only the first powersource 206 or only the first and second power sources 206 and 208 aresupplying DC power to the load 204.

For example, the first power source 206 has the highest load priority(Priority 1). The first power source 206 may supply DC power to the load204 when the load demand starts. As the load demand increases to reachand exceed the output capacity (e.g., maximum output capacity) of thefirst power source 206, the first power source 206 will enter constantcurrent (CC) or constant power (CP) mode. In this mode, the first powersource may continuously supply a full rated current/power capacity ofthe first power source 206 to the load 204.

As the load demand increases beyond the output capacity of the firstpower source 206, the second power source 208 will start supplying andsharing the DC power demanded by the load 204. At this point, both thefirst power source 206 and the second power source 208 are supplying DCpower to the common load 204. The first power source 206 is operating inthe CC/CP protection mode while the second power source 208 determinesthe DC output voltage to the load 204. At this stage, the second powersource 208 is operating in a constant voltage (CV) regulation mode.

As the load demand further increases to reach and exceed an outputcapacity of the second power source 208, the second power source 208will enter into a constant current (CC) or constant power (CP)protection mode, where the second power source 208 may continue tosupply the full rated current/power capacity of the second power source208 to the load 204. At this point, the first power source 206 and thesecond power source 208 are both operating in CC/CP protection mode andsupplying their full combined current/power capacity to the load 204.

As the load demand further increases beyond the combined capacity of thefirst and second power sources 206 and 208, the third power source 210will start supplying and sharing the power demanded by the load 204. Atthis point, the first and second power sources 206 and 208 are bothoperating in the CC/CP protection mode while the third power source 210determines the DC output voltage to the load 204 by operating in aconstant voltage (CV) regulation mode, and all three power sources 206,208 and 210 are sharing and delivering power to the load 204.

As the load demand further increases beyond the total combined capacityof the three power sources 206, 208 and 210, the third power source 210will enter the CC/CP protection mode so that all three power sources206, 208 and 210 are operating in the CC/CP protection mode, and theoutput voltage may be determined by load impedance.

In the opposite direction, as the load demand decreases (e.g., below thecombined output capacity of all three power sources 206, 208 and 210),the third power source 210 will exit the CC/CP protection mode and willdetermine the DC output voltage by operating in the CV mode. As the loaddemand further decreases (e.g., below the combined output capacity ofthe first and second power sources 206 and 208), the third power source210 may be completely unloaded (e.g., stop supplying DC power to theload 204). In this case, the second power source 208 will exit the CC/CPprotection mode and will determine DC output voltage by operating in theCV mode.

As the load demand further decreases (e.g., below the output capacity ofthe first power source 206), the second power source 208 may becompletely unloaded (e.g., stop supplying power to the load 204). Inthis case, the first power source 206 will exit the CC/CP protectionmode and will determine DC output voltage by operating in the CV mode.

As described above, the load sharing sequence of the three power sources206, 208 and 210 may be determined by different priority levels (e.g.,priority settings) of the three power sources 206, 208 and 210. Forexample, the three power sources 206, 208 and 210 may implement droopcurrent sharing control as illustrated in FIG. 3.

FIG. 3 illustrates individual droop V-I characteristics (e.g., droopload lines) of the individual power sources 206, 208 and 210.Specifically, region 207 is a droop V-I characteristic of the firstpower source 206, region 209 is a droop V-I characteristic of the secondpower source 208, and region 211 is a droop V-I characteristic of thethird power source 210.

As shown in FIG. 3, the droop V-I characteristics of the three powersources 206, 208 and 210 may coincide with one another. For example, alower droop load line threshold of the first power source 206 is thesame as an upper droop load line threshold of the second power source208. Similarly, a lower droop load line threshold of the second powersource 208 is the same as an upper droop load line threshold of thethird power source 210. Therefore, the combined droop load line of thethree power sources 206, 208 and 210 represents a continuous straightline without a gap or an overlap.

In other embodiments, the combined droop load line of the three powersources 206, 208 and 210 may be different from a continuous straightload line. For example, the upper and lower thresholds of adjacent powersources may overlap one another, the upper and lower thresholds ofadjacent power sources may be spaced from one another by a gap, etc. Insome cases, the slope of the combined droop load line may be differentfrom the slope illustrated in FIG. 3.

In one specific example, the first power source 206 may include an upperthreshold of 365V and a lower threshold of 359V, the droop load line ofthe second power source 208 may include an upper threshold of 359V and alower threshold of 356V, and the droop load line of the third powersource 210 may extend down from an upper threshold of 356V.

Because the different power sources 206, 208 and 210 have differentvoltage regulation settings, each power source 206, 208 and 210 maymaintain an enabled on-state during a period where the power source isnot supplying power to the load 204. For example, the power sources 208and 210 may maintain an enabled on-state during a period where only thefirst power source 206 is supplying DC power to the load 204. This mayoccur because the first power source 206 is regulating the voltage at adroop load line voltage setting of the first power source (e.g., 365V to359V) that is higher than the droop load line voltage setting of thesecond power source 208 (e.g., 359V to 356V) and the third power source210 (e.g., below 356V).

Once the voltage at the output 202 drops to a droop load line voltagesetting range of the second power source 208 (e.g., 359V to 356V)because a demand of the load 204 has exceeded the capacity of the firstpower source 206 to maintain the output voltage at the higher droop loadline voltage setting range of the first power source 206 (e.g., 365V to359V), the second power source 208 may start supplying DC power to theload 204 without receiving a command from the load 204, without enablingor disabling one of the power sources 206, 208 and 210, withoutconnecting or disconnecting one of the power sources 206, 208 and 210from the output 202, etc.

Similarly, the third power source 210 may maintain an enabled on-stateduring a period where only the first and second power sources 206 and208 are supplying power to the load 204. This may occur because thesecond power source is regulating the DC output voltage in the droopload line voltage setting range of the second power source (e.g., 359Vto 356V) that is higher than the droop load line voltage setting rangeof the third power source 210 (e.g., below 356V).

Once the voltage at the output 202 drops to the droop load line voltagesetting range of the third power source 210 (e.g., below 356V) because ademand of the load 204 has exceeded the capacity of the combined firstand second power sources 206 and 208 to maintain the DC output voltagein the higher droop load line voltage setting range of the second powersource 208 (e.g., 359V to 356V), the third power source 210 may startsupplying DC power to the load 204 without receiving a command from theload 204, without enabling or disabling one of the power sources 206,208 and 210, without connecting or disconnecting one of the powersources 206, 208 and 210 from the output 202, etc.

FIG. 4 illustrates an electrical power system 400 according to anotherexample embodiment of the present disclosure. The electrical powersystem 400 is similar to the electrical power system 200 of FIG. 2, butthe electrical power system 400 operates according to an active currentshare control.

Specifically, the electrical power system 400 includes an output 402 forsupplying a DC output voltage to a load 404, a first power source 406connected with the output 402, a second power source 408 connected withthe output, and the third power source 410 connected with the output402.

The first power source 406 includes a first load share bus 413, thesecond power source 408 includes a second load share bus 415, and thethird power source 410 includes a third load share bus 417. The loadshare buses 413, 415 and 417 are independent of one another and are nottied together (e.g., connected with one another, etc.).

Load share buses having different priority levels are preferably nottied up together to avoid violating a priority load share scheme.However, power sources at the same priority level may have their loadshare buses tied up together to provide active current sharing among thepower sources at the same priority level. For example, if six differentpower supply units (PSUs) have the same priority level, the load sharebuses of each of the six different PSUs may be tied up together as asingle common load share bus.

FIG. 5 illustrates individual active current control V-I characteristics(e.g., load lines) of the individual power sources 406, 408 and 410.Specifically, region 407 is a V-I characteristic of the first powersource 406, region 409 is a V-I characteristic of the second powersource 408, and region 411 is a V-I characteristic of the third powersource 410.

As shown in FIG. 5, an output voltage regulation setting of the firstpower source 406 is greater than an output voltage regulation setting ofthe second power source 408. The output voltage regulation setting thefirst power source 406 is separated from the output voltage regulationsetting the second power source 408 by at least a specified guard bandvalue to inhibit interaction of the first power source 406 and thesecond power source 408 (e.g., interaction of the first load share bus413 and the second load share bus 415). As one example, the outputvoltage regulation setting of the first power source 406 is 12.6V andthe output voltage regulation setting of the second power source 408 is12.4V.

Under this example priority load sharing scheme using active currentcontrol, each power source 406, 408 and 410 may have a separate loadshare bus and output voltage regulation setting. As descried in theexample above, the higher priority first power source 406 (i.e.,Priority1) may regulate the output to a higher DC voltage (e.g., 12.6V),as compared to the lower priority sources 408 and 410.

The second power source 408 (i.e., Priority2) may regulate the output toa DC voltage (e.g., 12.4V) that is lower than the output voltageregulation setting of the first power source 406 but higher than theoutput voltage regulation setting of the third power source 410. Thethird power source 410 (i.e., Priority3) may regulate the output to a DCvoltage (e.g., 12.0V) that is lower than the higher priority sources 406and 408.

Because the different power sources 406, 408 and 410 have differentoutput voltage regulation settings, each power source 406, 408 and 410may maintain an enabled on-state during a period where the power sourceis not supplying DC power to the load 404. For example, the powersources 408 and 410 may maintain an enabled on-state during a periodwhere only the first power source 406 is supplying DC power to the load404. This may occur because the first power source 406 is regulating thevoltage at an output voltage regulation setting of the first powersource (e.g., 12.6V) that is higher than the output voltage regulationsettings of the second power source 408 (e.g., 12.4V) and the thirdpower source 410 (e.g., 12.0V).

Once the voltage at the output 402 drops to the output voltageregulation setting of the second power source 408 (e.g., 12.4V) becausea demand of the load 404 has exceeded the capacity of the first powersource 406 to maintain the DC output voltage at the higher outputvoltage regulation setting of the first power source 406 (e.g., 12.6V),the second power source 408 may start supplying DC power to the load 404without receiving a command from the load 404, without enabling ordisabling one of the power sources 406, 408 and 410, without connectingor disconnecting one of the power sources 406, 408 and 410 from theoutput 402, etc.

Similarly, the third power source 410 may maintain an enabled on-stateduring a period where only the first and second power sources 406 and408 are supplying DC power to the load 404. This may occur because thecombined first and second power sources 406 and 408 are regulating theDC output voltage at an output voltage regulation setting of the secondpower source (e.g., 12.4V) that is higher than the output voltageregulation setting of the third power source 410 (e.g., 12.0V).

Once the voltage at the output 402 drops to an output voltage regulationsetting of the third power source 410 (e.g., 12.0V) because a demand ofthe load 404 has exceeded the capacity of the combined first and secondpower sources 406 and 408 to maintain the DC output voltage at thehigher output voltage regulation setting of the second power source 408(e.g., 12.4V), the third power source 410 may start supplying DC powerto the load 404 without receiving a command from the load 404, withoutenabling or disabling one of the power sources 406, 408 and 410, withoutconnecting or disconnecting one of the power sources 406, 408 and 410from the output 402, etc.

In some embodiments, a load share bus voltage on each power source 406,408 and 410 may have a same load share bus voltage definition (e.g., 8Vat a full rated current of the power source). However, the load sharebus of each power source 406, 408 and 410 may only be connected withpower supplying device(s) within that same power source (e.g., havingthe same priority level). The load share buses of different prioritypower sources may not be connected together.

Priority levels may be assigned to the power sources 406, 408 and 410 aspart of a system power distribution plan. For example, AC-DC rectifiersmay be defined as Priority1 source(s) (i.e., primary), while backupbattery units (BBUs) may be defined as Priority2 source(s) (i.e.,secondary).

In some cases, the system 400 may perform load scheduling based on ademand from the load 404, and may enable and disable power sources thatsupport a peak power load condition without exceeding an input ratedpower from a utility of a primary (e.g., Priority1) source.

FIG. 6 illustrates an electrical power system 600 according to anotherexample embodiment of the present disclosure. The electrical powersystem 600 is similar to the electrical power system 200 of FIG. 2, butthe first power source 606 of the power system 600 includes six powersupply units PSU1, PSU2, PSU3, PSU4, PSU5 and PSU6. The second powersource 608 includes six battery backup units BBU1, BBU2, BBU3, BBU4,BBU5 and BBU6.

As shown in FIG. 6, positive output terminals of the six power supplyunits of the first power source 606 and the six battery backup units ofthe second power source 608 are tied together (e.g., connected with oneanother) to supply DC power to the common load 604. Similarly, negativeoutput terminals of the six power supply units of the first power source606 and the six battery backup units of the second power source 608 aretied together.

In one example, a droop load line of the six power supply units of thefirst power source 606 extends from about 365V to about 359V, and adroop load line of the six battery backup units of the second powersource 608 (which has a lower priority than the first power source 606)extends from about 359V to about 356V.

In this case, the six power supply units of the first power source 606will share the load demand via a droop current share method along thedroop load line from 365V to 359V. At 359V, the output capacity of thefirst power source 606 is exhausted, and the first power source 606enters a protection mode of CC/CP while continuing to deliver the fulloutput capacity of the first power source 606.

As the load demand increases, the six backup battery units of the secondpower source 608 (having the lower priority) will start to deliver DCpower to the common load 604 in addition to the power delivered to theload 604 from the first power source 606. At this point, the six backupbattery units of the second power source 608 dictate the DC outputvoltage, and all the power supply units and the battery backup unitsshare and deliver power to the load 604.

At 356V, the total combined output capacity of the first and secondpower sources 606 and 608 is exhausted, and the first and second powersources will both be in a protection operation mode. In the oppositedirection, as the load demand decreases the DC output voltage will trackback from 356V to 365V until the protection modes of both power sources606 and 608 are disabled and the load demand goes low.

FIG. 7 illustrates an electrical power system 700 according to anotherexample embodiment of the present disclosure. The electrical powersystem 700 is similar to the electrical power system 600 of FIG. 6, butthe electrical power system 700 operates according to an active currentshare control.

A first power source 706 of the electrical power system 700 includes sixpower supply units PSU1, PSU2, PSU3, PSU4, PSU5 and PSU6, and a firstload share bus 713. The second power source 708 includes six batterybackup units BBU1, BBU2, BBU3, BBU4, BBU5 and BBU6 and a second loadshare bus 715.

In one example, the first power source 706 has a primary priorityvoltage setting (e.g., 12.6V), and the second power source 708 has asecondary priority voltage setting (e.g., 12.4V). As shown in FIG. 7,positive output terminals of the six power supply units of the firstpower source 706 and the six battery backup units of the second powersource 708 are tied together (e.g., connected with one another) tosupply power to a common load 704. Similarly, negative output terminalsof the six power supply units of the first power source 706 and the sixbattery backup units of the second power source 708 are tied together.

In this example, all six power supply units of the first power source706 will share the load demand in an active current share method via thefirst load share bus 713 with the primary priority voltage setting(e.g., 12.6V). At a peak load share voltage on the first load share bus713 (e.g. 8V), the output capacity of the first power source 706 isexhausted.

The load share voltage of each of the load share buses 713 and 715 maybe independent of the output voltage, because the load share voltagerepresents a load current. In one example, a full load current may berepresented by a peak (e.g., maximum) load share voltage of 8V. In thatcase, a half load current would be represented by 4V.

The load share buses 713 and 715 are not tied together, so they may usethe same load share voltage thresholds (e.g., 8V at a full loadcurrent). Alternatively, the load share buses 713 and 715 may usedifferent load share voltage thresholds (e.g., a peak load share voltageon the bus 713 may be 8V while a peak load share voltage on the bus 715is 6V).

Once the peak load share voltage is reached on the first load share bus713, the first power source 706 may enter a protection operating mode ofconstant power or constant current while delivering a full outputcapacity of the first power source 706.

As the load demand increases, the second power source 708 (having alower priority) will start to deliver DC power to the common load 704 inaddition to the first power source 706. At this point, the six batterybackup units of the second power source 708 dictate a DC output voltageof 12.4V based on the voltage setting of the second power source 708.All six power supply units of the first power source 706 and all sixbattery backup units of the second power source 708 now share and supplyDC power to the load.

At a peak of the voltage of the second load share bus 715 (e.g., 8V),the total combined output capacity of the first and second power sources706 and 708 is exhausted and the first and second power sources 706 and708 will both operate in a protection mode. In the opposite direction,as the load demand decreases the DC output voltage will track back tothe voltage setting of the first power source 706 (e.g., 12.6V) untilthe protection modes of both power sources 706 and 708 are disabled andthe load demand goes low.

FIG. 8 illustrates a line graph 800 of another example priority loadshare architecture operating according to a droop current share method.In the normal operating mode 820, one or more power supply units (PSUs)have a primary priority setting and share a droop load line of 365V downto 359V. As the load demand increases, the PSUs fall into a constantpower protection mode.

At this point, one or more battery backup units take over the busvoltage in a peak power operating mode 822, and the battery backupunit(s) range the bus voltage from 359V down to 356V. In the peak poweroperating mode 822, the combined PSUs and battery backup unit(s) deliverDC power to the load. The DC output voltage will track back from 356V upto 365V as the load demand ramps down.

FIG. 9 illustrates an electrical power system 900 according to anotherexample embodiment. The electrical power system 900 includes a firstpower source 906 including six power supply units PSU1, PSU2, PSU3,PSU4, PSU5 and PSU6. The electrical power system also includes a secondpower source 908 including six battery backup units BBU1, BBU2, BBU3,BBU4, BBU5 and BBU6. The power sources 906 and 908 may be similar to thepower sources 606, 608, 706 and 708 illustrated in FIGS. 6 and 7.

As shown in FIG. 9, each power source 906 and 908 includes mountingbrackets 920. Therefore, each power source power source 906 and 908 israck-mountable in an equipment rack, such as a power distribution rack,etc. Although FIG. 9 illustrates each power source 906 and 908 asincluding two mounting brackets 920 each, other embodiments may includemore or less mounting brackets 920, mounting brackets positioned atother locations on the power sources 906 and 908, mounting bracketsincluding more or less than two holes, etc.

The example electrical power sources described herein may include anysuitable sources for supplying power to a load, such as a DC-to-DCswitched-mode power supply, an AC-to-DC switched-mode power supply(e.g., a rectifier), a utility grid supply, a generator, a solar powergeneration source, a wind power generation source, and a battery, etc.

In some cases, a power source may include multiple components such as anAC-to-DC converter connected with a utility grid supply, DC-to-DCconverter coupled to a battery (e.g., a backup battery unit (BBU)), aDC-to-DC converter coupled to a solar or wind power generation source,etc. An electrical power system may include power sources of differenttypes, power sources of the same type, etc.

The power sources may be configured to perform operations using anysuitable combination of hardware and software. For example, the powersources may include any suitable circuitry, logic gates,microprocessor(s), computer-executable instructions stored in memory,etc. operable to cause the power sources to perform actions describedherein (e.g., supplying power to a load in a constant voltage mode, aconstant current mode, etc.).

As described above, a lower priority power source may continue tomaintain an enabled on-state (e.g., hot state) even when the powersource is not currently delivering DC power to the load. Therefore, thepower source may be ready to deliver power to the load at any time loaddemand increases beyond a load capacity of a higher priority powersource.

A power source may not require any command from the load to startsupplying DC power to the load (or stop supplying power to the load).The power source may respond independent of the load or other powersources. For example, each power source may follow a predefined droopload line voltage for droop current sharing and a predefined load sharevoltage for active current sharing. Because load sharing decisions mayoccur independently and simultaneously, power sources in exampleembodiments described herein may respond faster and adapt to fast loadtransients more quickly than power systems that require control commandsto enable and disable different power sources.

In some embodiments, power sources may provide automatic priority loadsharing without receiving a command from the load, without disabling oneof the power sources, without disconnecting one of the power sourcesfrom the output of the power system, etc. For example, power sources ofall priority levels may be tied up (e.g., connected together) andpowered on continuously without requiring monitoring of the powersources or load demand, without requiring turning on and turning offdifferent power sources, without requiring disconnecting different powersources from an output bus, etc. Therefore, some power sources mayprovide automatic (e.g., automated) priority load sharing.

In some embodiments, a power source priority level may be defined simplyby a priority voltage setting (e.g., different droop load lines in adroop current share method, different load share bus voltage settings inan active current share method, etc.). The power source priority levelmay be set to an initial priority sequence, and the priority sequence ofthe power sources may be changed during operation of the power system.

In some cases the priority of power sources is predefined prior tooperation of the power system and does not need to be updated on thefly. For example, a power system may include a power supply unit (PSU)and a battery backup unit (BBU), where the PSU is always the primarypower source and the BBU is always the secondary power source becausethe BBU may have a limited and time-bounded capacity.

Another example is a power system that requires peak power, where a PSUsupplies power during a normal load demand and a BBU supplies a peakpower during a peak load demand. This system may provide an advantage offully utilizing a PSU power system and infrastructure while transferringexcess power capacity to a BBU for peak power requirements.

In cases where primary and secondary power sources are similar or thesame (e.g., both sources are PSUs), the power system may command thedifferent power sources to change priority levels. When the systemcommands a primary PSU to become a secondary PSU, the primary PSU maychange its specified output voltage regulation setting down to aspecified output voltage regulation setting of the secondary PSU (e.g.,reduce from 12.6V to 12.4V). Similarly, the secondary PSU may increaseits specified output voltage regulation setting up to the specifiedoutput voltage regulation setting of the secondary PSU (e.g., increasedfrom 12.4V to 12.6V).

In some embodiments, priority of power sources may be changed forpreventative maintenance on a primary power source where the primarypower source is still capable of delivering limited power. In this case,the primary power source may be set as a secondary power source whilethe power source is in preventative maintenance. This approach couldalso apply to preventative maintenance for BBUs.

As another example, priority of power sources may be changed forreliability, to address degradation, etc. A primary power source thatalways delivers power to a load has a higher usage than a secondarypower source. In order to balance uneven usage of different powersources, the priority of the different power sources may be rotated.

The example power systems described herein may be used in any suitableapplication, including a hyperscale application where a grid powered PSUis load sharing with a BBU, multiple BBUs in arotating/alternating/changing load share priority, multiple BBUs in apower system delivering DC power to a common load, etc. For example,each BBU could have a different priority level to balance out a numberof discharge cycles per BBU, to operate a new BBU in load sharing withan old BBU, etc.

Example embodiments described herein may use a common load share controlmethod for all power sources having different priority levels, which mayincrease development and testing leverage (e.g., PSUs and BBU may havethe same interface and control, etc.). A common protection scheme may beapplicable to power sources having different priorities (e.g., a sameconstant power or constant current scheme for both a PSU and a BBU,etc.).

According to another aspect of the present disclosure, a method ofprioritizing load sharing in an electrical power system is disclosed.The electrical power system including an output for supplying a DCoutput voltage to a load, a first power source connected with theoutput, and a second power source connected with the output.

The method includes supplying DC power to the load using only the firstpower source when a demand of the load is less than an output capacityof the first power source, and supplying DC power to the load using boththe first power source and the second power source when a demand of theload is greater than an output capacity of the first power source. Themethod also includes maintaining the second power source in an enabledon-state when only the first power source is supplying DC power to theload.

In some embodiments, supplying DC power to the load using only the firstpower source may include operating the first power source to regulatethe DC output voltage in a constant voltage regulation mode. SupplyingDC power to the load using both the first power source and the secondpower source may include operating the first power source in a constantcurrent or constant power mode and operating the second power source toregulate the DC output voltage in a constant voltage regulation mode.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the disclosure. Individual elements or featuresof a particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the disclosure, and all such modificationsare intended to be included within the scope of the disclosure.

The invention claimed is:
 1. An electrical power system comprising: anoutput for supplying a DC output voltage to a load; a first power sourceconnected with the output for generating DC power, the first powersource configured to: regulate the DC output voltage to the load in aconstant voltage regulation mode when a demand of the load is less thanan output capacity of the first power source, transition from theconstant voltage regulation mode to a constant current or constant powermode in response to the demand of the load increasing from a value lessthan the output capacity of the first power source to a value greaterthan the output capacity of the first power source, and transition fromthe constant current or constant power mode to the constant voltageregulation mode in response to the demand of the load decreasing from avalue greater than the output capacity of the first power source to avalue less than the output capacity of the first power source; and asecond power source connected with the output for generating DC power,the second power source configured to: regulate the DC output voltage ina constant voltage regulation mode when the first power source isoperating in the constant current or constant power mode, and maintainan enabled-on state where the second power source is on but notsupplying DC power to the load when the first power source is operatingin the constant voltage regulation mode; wherein the electrical powersystem is configured to supply DC power to the load using only the firstpower source when the first power source is in the constant voltageregulation mode, and using both the first power source and the secondpower source when the first power source is in the constant current orconstant power mode.
 2. The system of claim 1, wherein: the second powersource is configured to start supplying DC power to the load in responseto the demand of the load increasing from a value less than the outputcapacity of the first power source to a value greater than the outputcapacity of the first power source; and the second power source isconfigured to stop supplying DC power to the load in response to thedemand of the load decreasing from a value greater than the outputcapacity of the first power source to a value less than the outputcapacity of the first power source.
 3. The system of claim 1, furthercomprising a third power source connected with the output to supply DCpower to the load, wherein: the electrical power system is configured tosupply DC power to the load using only the first power source and thesecond power source when a demand of the load is greater than the outputcapacity of the first power source and less than a combined outputcapacity of the first power source and the second power source; and thethird power source is configured to maintain an enabled on-state whenonly the first power source and the second power source are supplying DCpower to the load.
 4. The system of claim 1, wherein a lower thresholdof a droop load line of the first power source is equal to an upperthreshold of a droop load line of the second power source.
 5. The systemof claim 4, wherein the droop load line of the first power sourceincludes an upper threshold of 365V and a lower threshold of 359V, andthe droop load line of the second power source includes an upperthreshold of 359V and a lower threshold of 356V.
 6. The system of claim1, wherein a lower threshold of a droop load line of the first powersource is less than an upper threshold of a droop load line of thesecond power source.
 7. The system of claim 1, wherein a lower thresholdof a droop load line of the first power source is greater than an upperthreshold of a droop load line of the second power source.
 8. The systemof claim 1, wherein: the first power source includes multiple powersupplying devices connected with a first load share bus; the secondpower source includes multiple other power supplying devices connectedwith a second load share bus; and an output voltage regulation settingof the first power source is greater than an output voltage regulationsetting of the second power source.
 9. The system of claim 8, whereinthe output voltage regulation setting of the first power source is 12.6Vand the output voltage regulation setting of the second power source is12.4V.
 10. The system of claim 8, wherein the output voltage regulationsetting of the first power source is separated from the output voltageregulation setting of the second power source by at least a specifiedguard band value to inhibit interaction of active current sharingcontrol of the first load share bus and active current sharing controlof the second load share bus.
 11. The system of claim 1, wherein thefirst power source and the second power source each include at least oneof a DC-to-DC switched-mode power supply, an AC-to-DC switched-modepower supply, a utility grid supply, a generator, a solar powergeneration source, a wind power generation source, and a battery. 12.The system of claim 11, wherein the first power source includes aswitched-mode power supply and the second power source includes a backupbattery unit.
 13. The system of claim 12, wherein the first power sourceincludes six switched-mode power supplies connected in parallel, and thesecond power source includes six backup battery units connected inparallel.
 14. The system of claim 1, wherein the power supply system isconfigured to switch the first power source to a secondary prioritysetting and switch the second power source to a primary prioritysetting, during operation of the power system.
 15. The system of claim1, wherein the first power source and the second power source are eachconfigured to selectively supply DC power to the load without receivinga command from the load, and without disconnecting one of the powersources from the output.
 16. An electrical power system comprising: anoutput for supplying a DC output voltage to a load; a first power sourcecoupled with the output to supply DC power to the load; and a secondpower source coupled with the output to supply DC power to the load;wherein the electrical power system is configured to supply DC power tothe load using only the first power source when a demand of the load isless than an output capacity of the first power source, and the firstpower source and the second power source are each configured toselectively supply DC power to the load without receiving a command fromthe load and without disconnecting one of the power sources from theoutput, and wherein the first power source is further configured totransition to a constant current or constant power mode in response tothe demand of the load increasing from a value less than the outputcapacity of the first power source to a value greater than the outputcapacity of the first power source, and transition from the constantcurrent or constant power mode to the constant voltage regulation modein response to the demand of the load decreasing from a value greaterthan the output capacity of the first power source to a value less thanthe output capacity of the first power source.
 17. A method ofprioritizing load sharing in an electrical power system, the electricalpower system including an output for supplying a DC output voltage to aload, a first power source connected with the output, and a second powersource connected with the output, the method comprising: in a constantvoltage regulation mode, supplying DC power to the load using only thefirst power source when a demand of the load is less than an outputcapacity of the first power source; transitioning from the constantvoltage regulation mode to a constant current or constant power mode inresponse to the demand of the load increasing from a value less than theoutput capacity of the first power source to a value greater than theoutput capacity of the first power source; in the constant current orconstant power mode, supplying DC power to the load using both the firstpower source and the second power source when a demand of the load isgreater than an output capacity of the first power source; transitioningfrom the constant current or constant power mode to the constant voltageregulation mode in response to the demand of the load decreasing from avalue greater than the output capacity of the first power source to avalue less than the output capacity of the first power source; andmaintaining the second power source in an enabled on-state where thesecond power source is on but not supplying DC power to the load whenonly the first power source is supplying DC power to the load.
 18. Themethod of claim 17, wherein: supplying DC power to the load using onlythe first power source includes operating the first power source toregulate the DC output voltage in a constant voltage regulation mode;and supplying DC power to the load using both the first power source andthe second power source includes operating the first power source in aconstant current or constant power mode and operating the second powersource to regulate the DC output voltage in a constant voltageregulation mode.